Moved InvA to sign block; simplified fmaexpadd coding

pipelined/src/fpu/fma.sv

@@ -72,7 +72,7 @@ module fma(
     // Alignment shifter
     ///////////////////////////////////////////////////////////////////////////////
     // calculate the signs and take the opperation into account
-    fmasign sign(.OpCtrl, .Xs, .Ys, .Zs, .Ps, .As);
+    fmasign sign(.OpCtrl, .Xs, .Ys, .Zs, .Ps, .As, .InvA);
 
     fmaalign align(.Ze, .Zm, .XZero, .YZero, .ZZero, .Xe, .Ye,
                 .Am, .ZmSticky, .KillProd);

pipelined/src/fpu/fmaadd.sv

@@ -33,6 +33,7 @@ module fmaadd(
     input logic  [3*`NF+5:0]    Am, // aligned addend's mantissa for addition in U(NF+5.2NF+1)
     input logic  [2*`NF+1:0]    Pm,       // the product's mantissa
     input logic                 Ps, As,// the product sign and the alligend addeded's sign (Modified Z sign for other opperations)
+    input logic                InvA,          // invert the aligned addend
     input logic                 KillProd,      // should the product be set to 0
     input logic                 ZmSticky,
     input logic  [`NE-1:0]      Ze,
@@ -40,7 +41,6 @@ module fmaadd(
     output logic [3*`NF+5:0]    AmInv,  // aligned addend possibly inverted
     output logic [2*`NF+1:0]    PmKilled,     // the product's mantissa possibly killed
     output logic                NegSum,        // was the sum negitive
-    output logic                InvA,          // do you invert the aligned addend
     output logic                Ss,          
     output logic [`NE+1:0]      Se,
     output logic [3*`NF+5:0]    Sm           // the positive sum
@@ -51,11 +51,6 @@ module fmaadd(
     // Addition
     ///////////////////////////////////////////////////////////////////////////////
    
-    // Negate Z  when doing one of the following opperations:
-    //      -prod +  Z
-    //       prod -  Z
-    assign InvA = As ^ Ps;
-
     // Choose an inverted or non-inverted addend - the one has to be added now for the LZA
     assign AmInv = InvA ? ~Am : Am;
     // Kill the product if the product is too small to effect the addition (determined in fma1.sv)

pipelined/src/fpu/fmaexpadd.sv

@@ -36,7 +36,10 @@ module fmaexpadd(
     output logic [`NE+1:0]      Pe       // product's exponent B^(1023)NE+2
 );
 
+   logic 			PZero;
+   
     // kill the exponent if the product is zero - either X or Y is 0
-    assign Pe = ({2'b0, Xe} + {2'b0, Ye} - {2'b0, (`NE)'(`BIAS)})&{`NE+2{~(XZero|YZero)}};
+   assign PZero = XZero | YZero;
+    assign Pe = PZero ? '0 : ({2'b0, Xe} + {2'b0, Ye} - {2'b0, (`NE)'(`BIAS)});
 
 endmodule

pipelined/src/fpu/fmasign.sv

@@ -33,7 +33,8 @@ module fmasign(
     input  logic [2:0]  OpCtrl,               // opperation contol
     input  logic        Xs, Ys, Zs,    // sign of the inputs
     output logic        Ps,     // the product's sign - takes opperation into account
-    output logic        As   // aligned addend sign used in fma - takes opperation into account
+    output logic        As,   // aligned addend sign used in fma - takes opperation into account
+    output logic        InvA // Effective subtraction: invert addend
 );
 
     // Calculate the product's sign
@@ -41,7 +42,8 @@ module fmasign(
     
     // flip is negation opperation
     assign Ps = Xs ^ Ys ^ (OpCtrl[1]&~OpCtrl[2]);
-    // flip if subtraction
+    // flip addend sign for subtraction
     assign As = Zs^OpCtrl[0];
-
+   // Effective subtraction when product and addend have opposite signs
+    assign InvA = As ^ Ps;
 endmodule